Tube-cutting machine



Jan. 8, 1929.

E. M. HAWKINS TUBE CUTTING MACHINE Filed June 15, 1927 S Sheets-Sheet l I N VEN TOR.

. l 1 l l I 1 1 o.

ATTORNEY E. M. HAWKINS TUBE CUTTING MACHINE Jan. 8, 1929.

Filed June 15, 1927 3 Sheets Sheet 2 IN VEN TOR.

ATTORNEY Jan. 8, 1929. 1,698,264 E. M. HAWKINS TUBE CUTTING MACHINE A TTORNEY Patented Jan. 8, 1929.

names STA-res rarest DFFECEQ EDGAR M. HAWKINS, OF ROCHESTER, NEW YORK, ASSIGBL'OB, '30 M. D, KNOVJLTON COM- PAN Y, OF ROCHESTER, NEW YORK, A CORPORATION 01 JQZERV YORK.

TUBE-CUTTING MACHINE.

Application fil ed June 15,

multiple sections of uniform length at each operation, and the object of the present invention is to simplify the construction and operation of the machine by the provision of electromagnetic means for pro ecting the cutting mechanism into the path of travel of the tubing, which means is also ell'ective for impartg an initial impulse to the cutting mechanism in the direction of travel of the tubing; the electromagnetic means being controlled by switch mechanism actuated by a trip device engaged by the tubing to close the switch to initiate the cutting operation, and special means being provided for returning the cutt mechanism to initial position after each cu g operation, said means also being effective to open the switch controlling the electromagnetic means. i I p The invention is illustrated in the accompar ing drawings, in which "ig. 1 is a front elevation of the machine." F g. 2 is a plan View thereof;

8 is'an end elevation. 7 i is an enlarged front elevation, partly ion, oi the switch mechanism.

is a sectional side elevation thereof. 6 is a detailed View of the means for electing the snap action of the switch.

Referring to the drawings, 1 indicates the supporth frame of the machine, which is generally like that disclosed in application Serial No. 196,351 aforesaid, and includes a. motor, not shown, for driving the arbor of the itter mechanism, disposed, and arranged as in said prior application. Mountedon top of the tram e1 are spaced pedestals 3, 3, in which is journalled a shaft 6, the outer. end of which shaft is supported in a bearing 5 on the end of a bracket 42 secured to the end oi the iramel.

' Keyed to the shaft 6 is a generally H-shaped trainecomprising side members 7, Tand a ross member 8 provided with journal bean 9, 9 at the ends of the side members 7, in

192*)". San; no, 198,963.

which bearings is supported the arbor 12 carrying the cutting mechanism, the outer end ofthe arbor being supported in a bearing 11 on the end of an arin'lO, which is keyed to the end of shaft i The cutting mechanism per se is preferably of the same type as that shown in the application aforesaid, including a gang of rotary saws, three in number as illustrated, 14, 14'

freely on the arbor 12, but is rotatably con.-

nected-with the latter by splines or ribs.

and 14", carried by a sleeve 13, which slides.

including a double pulley 20, 21 rotatably 1 n'iountodon sh at'tfi, the pulley being belted to a pulley on the motor shaft and the pulley 21 connected by a belt 22 with a pulley 23 on the arbor 12.

The machine is preferably provided wit ha mandrel 2 parallel with the-saw arbor, which mandrel may. form ,part of the tube making machine with which the cutting apparatus I constituting the present inventlon is associated, in which case the construction and arrangement or the arbor will be that disclosed in said prior application and is designed. to guide a continuously travelling tubing throughtho machine in such relationto the cutting mechanism th atthe latter i'nay be pr0- jected into the path of travel of the tubing and cut the same into multiple predetermined lengtha which sections are adapted to be stripped or discharged from the mandrel successirely at the conclusionpofeach cutting operationi Monntedon top of the frame 1 are spaced 'pedestalsSO, 30 which support ahorizontallydisposed bar 31, preferably square in cross section and extending longitudinally of the machine; Adjustable longitudinally of the bar 31 is a bracket 32havinga vertically extended sleeve 32, in which is secureda rod 34 on which is mounted for verticaladjust nient a frame 35 provided with a bearinghub on its front face, in which is mounted a pmtleii? which constitutes the axisof a rotary :trip plate and strippingdevice of the same general character as that shown in the aparm 57 is loosely mounted.

plication aforesaid, said device comprising a central hub to which are attached three radial arms 40, 41 and 42, the first of which constitutes the trip plate to be engaged by the end of the uncut tubing to initiate the control of the cutting mechanism. Also mounted on the pintle 37 is a plate 43 provided with three peripheral cam surfaces. 43 separated by notches, the peripheral edge of the plate being engaged by a roller 46 mounted on a lever 4e pivoted on a stud 45 secured to the upper part of the frame 35, the lower end of the lever 44 being attached to a spring 47, which is adj uste ably connected to the frame 35 by a screw bolt and nut connection 48, said spring serving to force the roller into pressure contact with the edge of plate 43 and to impartsuccessive rotatory movements of one hundred and twenty degrees to the radial arms or blades &0, 41 and 42.

Secured to the shaft or pintle 37 is a dog or wiping abutment 55, adapted to engage an upstanding ln g on bell crank 52 pivoted to rock lever 50, which, in turn, is pivoted at its lower end to a stud 51 secured to the rear face of frame 35. The bell crank 52 is normally held in engagement with a stop lug or pin 5e on lever 50, by means of the tension spring 53 attached to the horizontal arm of the bell crank at one end and to a pin projecting from the hub of lever 50, this arrangement causing the dog 55, when moved in an anti-clockwise direction, as shown in Fig. 1, to engage the lug on the bell crank and to swing the lever in a clockwise direction. When, however, the shaft 37 and the parts carried thereby are rotated inthe opposite direction, when it becomes necessary to adjust the relation of the radial blades 40,. 41 and 42 with. respectto the travelling tubing, the dog 55 engaging the lug'on the bell crank swings the latter on its pivot against the tension of spring 53 without effecting any swinging movement of lever 50. This arrangement permitsthe rcadjustment of the trip plate and the stripping blades or arms, should the latter get out of step for any reason.

The upper end of lever 50 is adjustably connected to a pull rod 56 which extends longitudinally of the machine and is connected.

at one end to an arm'57 loosely mounted on shaft 59 of a rotary quick action or snap switch. The switch mechanism comprises a generally circular casing 60provided wit-h a bracket member 60 by means of which it is bolted to the bar 31, said casing having a front closure 61 bolted thereto and having a central opening which constitutes one of the bearings for the shaft 59 upon which the rock i v 4 Splined to the shaft 59 is a disk G5which carries two spaced contact locks 64,64 which are secured in position by threadedstuds and nuts and are connected by a conductor strip. Mounted on spring arms62 and 62 secured to the inner 7 upper end adapted to be engaged by an up-;

ward extension 57 of lever 57, which lever normally held in. retracted position by a spring 58 anchored to rod 58 fastened to bar 31.

The specialniechanism for effecting quick operationof the switch to avoid sparking between the contacts, comprises a collar 71 secured to the shaft 59 and provided with a wedge-shaped lug 72 adapted to be engaged by the correspondingly wedge-shaped end of plunger 73 slidably mounted in a cylindrical housing formed as an integral part of the switch casing 60, the plunger comprising a rod 74 extending longitudinally through the housing 75 and being forced downward into engagement with the lug 72 by means of a helical spring 76 surrounding the rod and adjusted as to tension by means of a nut 77 engaging the screw threaded upper end of housing 75, the rod 7 4 being provided on its end with a nut by means of which the throw of the plunger is adjusted. WVhen the shaft- 59 of the switch mechanism is rotated. in

either direction, the wedge face of lug 72 in engagement with the corresponding wedge face of plunger 73 forces the plunger upward against the tension of spring 76 and, as soon as the high parts of the wedges pass each other, the tension of the spring causes the opposite wedge face of the plunger to engage the opposite edge of lug 72 and ii'nparts a quick partial rotation to the shaft 59 and the contact carrying disk secured thereto, thereby bringing about an instantaneous engagement or disengagement of the switch contacts to reduce arcing of the electric current between said contacts.

Mounted on a bracket 80 secured at the rear of frame 1 is an electromagnet 80, which oted near its opposite end to a bracket 8st Uli mounted on top of frame 1. Pivotedon a pin 88 intermediate the length of lever83 is a lift rod, preferably of turn buckle construction, comprising end sections 85 and 87 and an adjustable threaded sleeve '86 connecting said sections, the upper end of said lift rod being connected by a cross pin 89 to one of the side arms 7 of the swinging frame which supports the saw arbor. The lever 83 extended beyond the pivotal support in bracket 84: and

is provided at its end with a clevis in which,v

openings through which passes'an eye bolt 92.

provided with an adjustingnut 93, which eye bolt extends through an opening in'thetop of the frameland has anchored thereto one amount of energy required to be applied to the solenoid to this eirtent. By accurately adpistiii the tension of the spring 94- so that the pull of the spring' on the lever 83 is ust overbalanced by the weight of the swinging frame of the cutter mechanism, it will be nec-. essary to apply only a relatively small amount of current to the solenoid S0 to effect'the lifting of the of the cutter mechanisin'to bring the saws into ment with the tubing. I V

The solenoid is provided with terminal binding oosts which are connect-ed by leads 6'? and 67 with similar termiruils or binding,"

posts 66 and 66 on the front face of tho closurc 61 of the switch mechanism, which binding posts 66 and 66 are connected to the spring arms (32 and'62 carrying the fixed contacts 63 and 63 of the switch, so that,

when the contacts 6?,- and 63" are engaged by the contacts (i l and 6- 1 carried by the movable element of theswitch, the circuit to the solenoid is closcchthereby energizing thesoleno'id and causing its core 81 to move upward, raising lever 83 and swinging the frame carrying the saws upward until the saws are projected into the path of travel of the tubing.

The movement of the saws during the cutting operation, in the di-rect-ionof travel of the tubing, is effected by theengagement of the saws with the-tubing; that is to say, as

' soon asthe saws bite into the tubing, they,

with their supporting sleeve, are moved longitudinally of the arbor 12 at the same rateoi":

speed as the tubing, thereby'insuring a complete andclean cut by each of the saws. However, inasmuch as the saws and'certain coordinated moving partsrequire considerable energy to start their movement from a position of rest, it has been found expedient to provide means for imparting an initial 1mpulse or movement to the saws longitudinally of the arbor 12 and in the direction of movementof the tubing, 111st priorto theengagement of the saws with the tubing. This is offee-ted by means of-a rock lever 118 pivoted at" 1141- to the top of the machine frame, said rock lever having a vertical arm with a "clevised upper end straddlingthe arbor 12 and engag inp the end of the'sleeve 13 carryi or end by a pendent rod 112 mounted on tubing,

no the saws, .nd a horizontalurm which isengaged at its a out the latter, thereby rotating; shaft 59m mo e a horizontal pivot 111 journaled in'a bracket 110 secured to. the under face of one of the ournal bearings f the swinging saw ar-- bor frame, so that, when'said' frame is lifted to project the saws into the path of travel on its pivot by the lift rod 112 and thereby impart an initial kick or impulse to the saw carrying sleeve suiiicient to initiate the move- 'ment of t 1e same in the direction of travel of the tubing just before the saws engage the The means for returning the saws to initial position after each cutting operation coniprses a horizontally swinging 'lever 100, which may be conveniently for. 'ied of two straps of metal boltedtogether and splayed at their ends to constitute forks, one of which ispivoted to a collar 101 on shaft 6 andthe other to the yo'hedilze member 10% engaging groove 3 inthe saw carrying sleeve 13. This lever is actuatedin its movement to retract the sleeve 13 to initial position by means i of a spring 105 connected to said lever at a point intermediate the ends ofv the lat ter, said spring being adjustably anchored at its opposite end to an eyebolt 106 secured one arm 7 of the swinging frame carrying v the saw arbor, as more particularly illuslii2ttQfl111F1g. 2.

' 7 its hereinbeforestated, the saws during:

their cutting operation are moved longitudi nally of their supporting arbor by reason of their engagement with the tubing, and it is, therefore, necessary to disen'gags the saws from the tubing'after the completion of the cutting operation, to permit the saws to return to their 1n1tial position before tnenext cutting operation. This 'means that it is necessary to deenergize the magnet which has lifted thesaw' carrying frame to proyect thesaws into the path of movement er the tub mg and, in order to-efl'ect this desired result,

the following means are provided ,foroperatmg the switch mechanism to breal: the el- I 110 cultto the solenoid. The lever 70 connected tothe shaft 59 of the movable member of. the i i switch is extended downward and is provided at its lower end with an eye through which passes a rod 9'? having a ball-shaped head 98 on the end engaging; lever 70 and a ball 108 ad'ustablelon 'itud-inall of the leno'th of It will be seen, therefore, that asthe lever, I

100vmoves with the saws asthelattertravel with the tubing in the cuttingoperatioiuthe rod 97 slides through the eye in the lower end of the lever *Z'O'and, when the-head 98 on the end of the rod engages said lever, it swi s TU of the-tubing, the rock lever will be swung contacts 64, 64' out of engagementwith contacts 63, 63 and breaking the circuit to the solenoid, which permits the saw frame to drop and the spring 105 to quickly return the sleeve carrying the saws to its initial position. The rod 97 is so adjusted with respect to its engagement with lever 100 that said rod will effect the opening of the switch controlling the solenoid soon as the cutting operation has been completed, which adj ustment is effected by sliding the ball 108 along the rod and securing it to the rod by the setscrew, when the desired adjustment has been obtained. 3

Under certain conditions, it is desirable and necessary to suspend the cutting operation and to permit the tubing to be fed through the machine without being out, as, for example, when certain portions of the tubing are found to be defective or the machine becomes clogged for any reason. In order to bring about this result, there is provided a lever 120 pivoted at its lower end to the front of the frame 35 and provided intermediate its length with a latching lug 122 adapted to be moved into and out of engagement with a stop pin or detent 123 on the rear face of cam plate 43, which pin located diametrically opposite the trip arm l0, the lever being held in its two extreme positions by means of stop pins 121 and 121 fixed to frame 35, as more particularly shown in Fig. 1. When the lever is mo ved so that lug122 is in the path of movement of pin 123 on the cam plate, the next succeeding swinging movement of the trip device brings pin 123 into engagement with latching lug 122 and arrests the movement of the trip device with the several arms or blades thereof entirely out of the path of movement of the tubing, thereby suspending the operation of the trip device until the lever 120 is moved to its opposite position to release said trip device, which is thenreturned to its operative relation by the normal action of spring actuated lever 44, as hereinbefore GXPlELIIIQCl. fThe operation of the apparatus, as described, is asfollows: The tubing is fed into the machine in continuous lengths and is guided accurately in its feeding movement by the mandrel 2. the tubing engages trip plate 40, it imparts a partial rotation to said trip plate and shaft 37 on which said trip plate is mounted. The rotationof shaft 37 causes dog to engage bell crank 52 mounted on rocklever 50, thereby swinging said rock lever in the direction of movement of the'tubmg and imparting a forward movement to pull rod 56, which swings rock lever 57, loosely mounted on shaft 59 of the switch mechanism, against the tension of spring 58 and causesthe upper end 57 of said rock lever to engage the lateral extension of arm fast to the shaft of the switch mechanism, thereby causing a' par- When the front end of tial rotation of the shaft suflicient to bring the switch contacts into engagement, which engagement is accelerated by the snap action of the plunger 73 and the camming collar 71 on the shaft 59. The completion of the initial movement of the trip arm carries the lug out of engagement with the bell crank 52,therehy permitting the rock arm 50 to be returned to its normal position by spring 47 and rock lever 57 to be retracted from engagement with arm 71 of theswitch mechanism, leaving the switch in closed position. The closing of the switch energizes solenoid 80, which immediately attracts its'core 81, thereby rocking lever 83 and, through the turn buckle lift rodconnecting said lever with the saw frame, also swinging thelatter on the shaft 6 and lifting or projecting the saws into the path of travel of the tubing. The

initial lifting movement of the saw frame by the solenoid causes the rod 112 to rock bell crank 113 and impart an initial impulse 'or movement to the sleeve carrying the saws longitudinally of the saw arbor and in the direction of movement of the tubing, so that the tubing will be relieved of the otherwise heavy strain, which would be placed thereon in startin g the movement of the saws longitudinally of their arbor. As the saws are constantly rotated on their arbor and the tubing is rotated on the mandrel, the cutting operation is effected quite rapidly and the several sections of the tubing are severed simultaneously. As the end of the uncut tubing had imparted a partial rotation to the trip plate suflicient to bring theroller 46 on the spring actuated lever 44 into engagement with the cam section adjacent the trip arm, the spring applied pressure of the roller imparts a further rotatory movement to the shaft carrying the trip arm, thereby bringing the following radial armor blade 42 into engagement with the surface of the forward section of the tubing, so that, as soon as the latter has been completely severed, said arm l2 will strip or flipthe cut section off of the mandrel. The following cut section will then engage the arm or blade 42 and impart a further partial rotation to the shaft 37, which will cause the" spring arm 44; to impart a further kick or partial rotation to shaft 37, thereby causing blade 41 to engage the surface of the second out section of the tubing and flip the same from the mandrel by a corresponding movement produced by the engagement of the end of the third cut section with blade 41 imparting a partial rotation to shaft 37, which brings the trip arm 40 into engagement with the third by the advancing end of the uncut tubing,

ready for the next operation. When the cutting operation has been completed,'the sleeve carrying the saws has been movedalongthe arbor 12 by engagement of the saws with the tubing as described, thereby swinging lever 100 to the right, as shown in Fig. 2, said lever moving rod 97 with it until the ball on the op posite end of said rod engages-the pendent arm of lever 70 and 'ocksshaft 59 of the switch mechanism to disengage the switch contacts, the latter operation being -facilitated and accelerated by the snap action of the plunger 73 and the camming co11ar7l on the shaft 59, as hereinbefore described. The breaking of the circuit to the solenoid deenergizes the latter, releasing the core and permitting the frame carrying the saws to drop, at which time spring 105 swings lever .100 to the left, as shown in Fig. 2, thereby moving the sleeve 13 carrying th'esaws to its initial position. x

WhatIclaimis: 1. A tube cutting machine, comprising neans for guiding a travelling tubing throug 1 the machine, cutting means mounted for transverse and parallel'movements relative -means to open said switch afterthe tion of the cutting operation.

to the tubing, trip controlled electromagnetic means operative to project the cutting means into the path of travel of the tubing, and means operated by the projecting means to impart an initial impulse to the cutting means in the direction of travel of the tubing.

' 2. A tube cutting .machine, comprising means for guiding atravelling tubingthrough the machine, cuttingmeansmounted for trans verse and parallel movements relative to the,

tubing, an electromagnet operative to project the cutting means intothepath of travel of the transverse and parallel movements relative to thetubing, an electromagnet operative to project the cutting means into the path of travel of the tubing, means actuated by the advance of the tubing controlling the operation of said magnet, said means including a trip plate engaged by the tubing and a switch operatively connected to said trip plate, means actuated by the movement of the cut ting means to open said switch after the completion of the cutting operation, and means to return the cutting mechanism to initial inoperative position.

4:. A tube cutting machine, comprising means for guiding a travelling tubing through the machine, cutting means mounted for tubing, an electromagnet operative to project transverse and parallel movements relative to the tubing, anelectromagnet operative to project the cutting means into the path of travelof the tubing,.means actuated by the advance of the tubing controlling the operation of saidmagneusaid means including a trip plate engaged by the tubing and a switch operatively connected to said trip plate,

means actuated by the movement ofthe cutting means to open said switch after thecompletion of the cutting operation, and means .to. return the cutting mechanism toinitial inoperative. position comprising a pivoted arm connected to the cutting mechanism and a spring actuating said arm.

5. A tube cutting machine, comprising means for guiding atravellingtubing through the machine, cutting means mounted for transverse and parallel-movements relative to the the cutting meansinto the-path of trave .of

i the tubing, means actuated by the advance of the tubing controlling the operation of said magnet, said means including a trip plate engaged by the tubing. and. a switch operatively connected to said trip plate, means actuated by the movement of the cut.- ting means to open said switch after the completion of the cutting operation, and means to return the cutting mechanism to initial "inoperative position comprising a pivoted arm.

connected to the cutting mechanism and a spring actuating. said arm, said pivoted arm having an adjustable connection with the switch operating means.

.7 6. A tube cutting machine, comprising means for guiding a travelling tubing through the machine, a pivoted frame carrying a cutter arbor parallel with the path of travel of the tubing, cutting means sli'dable on thearbor, anelectromagnet operative to swing the frame and'move thecutting means intoengagement with thetubing, aswitch controlling said magnet, atrip device engaged by the end of the tubing connected to said switch for closing the latter, means, for returning the cuttingmechanism toinitial position, andmeans connectedwith said re turning means for opening the switch. A

7. A tube cutting mach ne, comprising meansfor guid ng a travelling tubing through the machine, a pivotedframe carrying a cutter arbor parallel with the path of travel of the; tubing, cutting means slidable .on the arbor, an electromagnet operative to swing the frame and move the cutting means into engagementwith the tubing, means actuated by the swinging movement of the frame to ward the tubing to initiate theslidingmOVement of the cutting means with the tubing, a switch controlling said magnet, a trip device engagedby the end'of the tubing connected to said switch for closing the latter,

means' -for returning the cutting mechanism to initialposition, and means connected initial movement to the cutting means with the tubing, a switch controlling said magnet,- a trip device'engaged by the end of the tubing connected to said switch for closing the latter, means for returning the cutting mechanism, to initial position, and means connected with said returning means for openlng the switch. e

9. A tube cutting machine, comprising means for guiding a travelling tubing through the machine, a pivoted frame, a saw carrying sleeve slidable on said frame, an electromagnet for movlng the frame toward the a tube guiding means, and means connected to the frame and actuated by the movement of the latter toward the tubing to impart an initial movement of the sleeve with the tub- 10. A tube cutting, machine, comprising means for guiding I a travelling tubing through the machine, a pivoted frame, a saw carrying sleeve slidable on said frame, an electromagnet for moving the frame toward the tube guiding means, a lift rod suspended from the frame, and a bell crank having one arm connected tosaid rod and the other engaging the sleeve; whereby the movement of the frame toward the tubing will cause the bell crank to start the movement of the sleeve with the tubing.

11. A tube cutting machine, comprising a mandrelfor guiding the tubing through the 'machine a pivoted frame, a saw carrying sleeve slidable on said frame, an electromagnet for swinging the frame toward the mandrel, a switch controlling the circuit to said magnet, a trip device operated by the travelling tubing to close the switch, means for re turning the sleeve to initial position, and means connected to said returning means for opening the switch. i

12. A tube cutting machine, comprising a mandrel for guiding the tubing through the machine, a pivoted frame, a saw carrying sleeve slidable on said frame, an electromagnet for swin ing the frame toward the mandrel, a switch magnet, a trip device operated by, the travelling tubing to close the switch, a spring actu ated lever pivoted to the frame and connected to the sleeve for returning the latter to inoperative position, and an adjustable pull rod controlling the circuit to said connecting said lever and the switch to open the latter after the completionof the cutting operation. l i

13. tube cutting machine, comprising a mandrel for guiding the tubing through the machine, a frame pivoted for swinging movement toward and fromthe mandrel, a saw carrying sleeve slidable on said frame, an

electromagnet for swinging the frame toward the mandrel, a rotary switch controlling the circuit to said magnet, said switch including an arm fast to the shaft therof and an arm loose on said shaft, a trip device operated by the travelling tubing, connections between the trip device and the loose arm on the switch shaft to close the switch, a spring actuated lever pivoted to the frame and connected to the sleeve for returning the latter to initial position, and connections between said lever and the arm fast to the switch shaft to open the switch.

14. A tube cutting machine, comprising a mandrel for guiding the tubing through the machine, a pivoted frame having an arbor parallel with the mandrel, a saw carrying sleeve slidable on the arbor,an electromagnet for movin the frame toward the mandrel, a switch inc uding a rotary shaft with a fixed arm and a cooperating loose arm thereon, a pivoted trip plate engaged by the end of the tubing, connections between the trip plate and said loose arm toswing the latter into engagement with the fixed arm to close the.

switch andenergize the electromagnet, a spring actuated lever pivoted to the frame and to the sleeve for returning the latter to initial position, and a pull rod adjustably connected to said lever and slidably connected to the arm fast to the switch shaft to open the switch after each cutting operation.

15. A tube cutting machine, comprising a mandrel, a pivoted frame, a saw carrying sleeve slidable on said frame in parallelism with the mandrel, an, electromagnet for swinging the frame toward the mandrel, a

switch controlling the circuit to said magnet, a rotary trip device engaged by the tubing and eflective to close said switch, means connected with said sleeve for returning the latter to initial position, and adjustable means connecting the returning means with the switch to open the latter after each cutting operation.

16. A tube cutting machine,comprising a mandrel, a pivoted frame, a saw carrying sleeve slidable on said frame in parallelism with the mandrel, an electromagnet for swinging the frame toward the mandrel, a switch controlling the circuit'to said magnet, a rotary trip device engaged by the tubing and effective to close said switch, means connecting said trip deviceand the switch to close the latter said means including a dog on the shaft of the trip device, a rock lever having a spring held detent in the path of said dog and operative to move the rock lever latter to initial positiom'and adjustable means when engaged by the dog in its normal operaconnecting the returning means with the tion and inoperative to move the lever upon switch to open the latter after each cutting 10 opposite movement of said dog, whereby said operation.

:1 trip device may be adjusted, and a pull rod In testimony whereof affix my signature.

connecting the rock leverand switch, means I connected with said sleeve for returningthe v EDGAR M. HAWKINS; 

